Divi Widget Builder Plugin displays source from wp_posts table

We are building a Divi based WP site for a client that has a custom portal application.

To make this work, in the portal we include wp_load.php, and we call get_header() and get_footer() as needed. This works, and standard widgets and other widgets work correctly, for example Text widget, and the Modern Tribe Image widget.

When using the Divi Widget Builder widget to put a Divi library item in the a footer section it works correctly on the standard WP pages, but what is displayed in the portal page footer is the verbatim content from the wp_posts post_content table for that item. For example:

My suspicion is that I’m missing an include or something, but I’m not sure where to go from here. There are no errors in the error log.